The energy and cost efficiency of aluminum smelting can be significantly reduced with the use of inert, non-consumable and dimensionally stable anodes. Replacement of traditional carbon anodes with inert anodes should allow a highly productive cell design to be utilized, thereby reducing capital costs. Significant environmental benefits are also possible because inert anodes produce no CO2 or CF4 emissions. Some examples of inert anode compositions are provided in U.S. Pat. Nos. 4,374,050, 4,374,761, 4,399,008, 4,455,211, 4,582,585, 4,584,172, 4,620,905, 5,794,112, 5,865,980, 6,126,799, 6,217,739, 6,372,119, 6,416,649, 6,423,204 and 6,423,195, assigned to the assignee of the present application. These patents are incorporated herein by reference.
Inert anodes must be electrically connected to conductors that are typically made of metal such as nickel, Inconel or steel. However, making a low voltage drop electrical connection between a metallic conductor and an inert anode comprising a ceramic or ceramic-metallic (cermet) is a challenge. The connection must be maintained with good integrity (low voltage drop) over a wide range of temperatures and operating conditions. One type of connection could utilize a precision mechanical connection between the ceramic anode and metal conductor, such that an interference is developed above a certain desired temperature. This type of connection has several drawbacks. It requires smooth surfaces and tight tolerances of both the metallic and ceramic surfaces, which can only be done with expensive precision machining. In addition, the connections must typically use matched anode/conductor sets, so the parts are not interchangeable. This type of connection also causes internal stresses on the anode, which could contribute to cracking or failure of the anode. Finally, the connection must be kept clean and free of foreign particles that would interfere with the contact.
The present invention has been developed in view of the foregoing.